My website based on Jekyll does not work with MathJax

Question

My problem

So you can have a look on my problem, see my blog post in this link: https://matheusrabetti.github.io/statistics/bayesian-introduction/

In the end of the post you can see this - "This can be represented with a beta distribution with parameters and ( \beta=219):"

Here my markdown file have the code: This can be represented with a beta distribution with parameters $$\alpha=81$$ and \( \beta=219\):

I was expecting to see the Tex formula, when using $$, on my website and it's returning a blank space.

My path until know

In my _includes folder - check my github repository here https://github.com/MatheusRabetti/matheusrabetti.github.io - I have the following code in the _scripts.html file:

<script type="text/x-mathjax-config">
MathJax.Hub.Config({
    tex2jax: {
  inlineMath: [['$','$'], ['\\(','\\)']],
  displayMath: [ ['$$','$$'], ['\\[','\\]'] ],
  processEscapes: true
     }
});
</script>

<script type="text/javascript"
   src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
</script> 

This javacript code has been in the _header.html and many other files.

I'm using the interpreter:

markdown: kramdown

My _layout posts files are including the _scripts.html:

{% include _scripts.html %}

</body>
</html>

Where my page is blank, inspecting the html page I found that:

The mean is
<script type="math/tex">
  \frac{\alpha}{\alpha + \beta} = \frac{81}{81+219} = 0.270
<\script>

As you can see I have little knowledge on Jekyll or Octopress and I will give more informations as the help comes, because I don't know what's the problem and what can help you.